RelativeResourceManager - Chapter 3 Receptors Receptors...

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Unformatted text preview: Chapter 3 Receptors Receptors •  receptor: a protein embedded in a cell membrane •  site of drug ac9on •  specialized •  serve a specific purpose •  Human cells average 50 receptors. •  many types and loca9ons The Nerve Cell dendrites ­receive signals cell body ­ processes info neurotransmiFers axon ­sends signals o o o o o o SYNAPSE ­gap synap9c vesicles axon impulse * * ** * * * * * * * * * * * vesicles open neurotransmiFers are released receptor cell travel to receptors Synap9c Neurotransmission Dopamine is available to bind to specific proteins called dopamine receptors hFp:// Structure of dopamine receptor hFp:// A. Receptor Site Theory •  •  one major explana9on for drug ac9vity drugs act at a specific receptor to produce a specific response •  Drug must have correct 1.  size 2.  shape 3.  electrical characteris9cs •  Lock & Key analogy •  agonist ­drug which fits a receptor and causes a response •  antagonist ­drug which fits a receptor but doesn’t cause a response •  naloxone/heroin analogy MORPHINE HEROIN NALOXONE (NARCAN) B. Drug ­receptor interac9ons Drugs and receptors are found in low concentra9ons in the body drug + receptor Kd = Kon Koff drug ­receptor complex [drug] [receptor] __________________________ [drug ­receptor complex] •  Receptors must be saturated for effect to take place. •  Eventually drug is displaced from binding sites: 1.  compe99on with another drug 2.  enzyme ­catalyzed destruc9on 3.  conc. of drug decreases as it is excreted •  Another dose must be taken to provide effect. Forces aFrac9ng drug to receptor: a)  Covalent bonds  ­strongest bond  ­rare b)  Ionic (or electrosta9c) interac9ons  ­physiological pH = 7.4  ­Carboxylic acids are deprotonated to give anions.  ­Amino groups are protonated to give ca9ons. O Drug H3N receptor O O Drug receptor NH3 O : c) Hydrogen bonds :  ­O ­H N :  ­N ­H O F Intramolecular H ­bond  ­ STRONGER! Intermolecular H ­bond O O H OCH3 O OCH3 methyl salicylate (oil of wintergreen) weak an9bacterial agent HO methyl p ­hydroxybenzoate more potent an9bacterial agent d) Charge ­transfer complexes good electron donor contain pi electrons or nonbonded electrons Donor groups alkenes alkynes aroma9c groups  ­O  ­N  ­S good electron acceptor electron deficient, pi orbitals Acceptor groups alkenes alkynes aroma9c groups acidic protons CN Cl Cl Cl Cl CN chlorothalonil (fungicide) OH e) Hydrophobic interac9ons  ­two nonpolar groups  ­don’t actually “dissolve” in one another  ­lower energy for nonpolar groups O butamben (topical anesthe9c) H2N O isoleucine f) Van der Waals (or London dispersion) forces  ­temporary  ­weak  ­must be close contact hydrophobic H ­bond ionic H H charge transfer or H ­bond N :N O CH3CH2CH2CH2O dipole ­dipole or H ­bond hydrophobic CH2CH2 N CH2CH3 CH2CH3 ...
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